1. Field of the Invention
The present invention relates to an electric power steering apparatus. More particularly, the present invention relates to a pinion sensor assembly, a pinion sensor cover assembly, and an electric power steering apparatus having the same that can reduce a measurement error caused by accumulation of assembly errors of constitutional components when a torque sensor and a neighboring element are assembled, thereby preventing a malfunction, and enhancing assemblability.
2. Description of the Prior Art
In general, a hydraulic power steering apparatus which uses hydraulic power of a hydraulic pump has been typically used as a power steering apparatus for a vehicle. However, recently, an electric power steering apparatus using a motor is gradually popularized.
An ordinary electric power steering apparatus includes a steering system extending from a steering wheel to opposite side vehicle wheels, and an assistant power mechanism for supplying steering assisting power to the steering system.
The assistant power mechanism includes: a torque sensor configured to sense a steering torque applied to the steering wheel by a driver and to output an electric signal which is proportional to the sensed steering torque; an electronic control unit (ECU) configured to generate a control signal based on the electric signal transmitted from the torque sensor; a motor configured to generate a steering assisting power based on the control signal transmitted from the ECU; and a belt type power transmission apparatus configured to transmit the assisting power generated by the motor to a rack bar through a belt.
FIG. 1 is a partial cross-sectional view schematically illustrating a rack-driving type power steering apparatus according to the prior art, and FIGS. 2a and 2b are a cross-sectional view and an exploded perspective view schematically illustrating a part of the rack-driving type power steering apparatus of the prior art.
As illustrated in the drawings, the rack-driving type power steering apparatus according to the prior art includes: a rack bar 140 extending in a transverse direction of the vehicle, and having a rack gear on a side of the outer peripheral surface thereof; a pinion shaft 110 provided with a pinion gear engaged with the rack gear; a ball nut 210 engaged with a outer peripheral screw flute 145 via balls 220; a belt type transmission apparatus 160 configured to interconnect the ball nut 210 and a motor spindle 155; and a motor 150.
The pinion shaft 110 is connected to the steering wheel through a steering shaft, and the rack bar 140, which is formed with the outer peripheral screw flute 145 with a predetermined length on a side of the outer periphery thereof, is incorporated in a rack housing 120.
The belt type transmission apparatus 160 includes a belt for interconnecting the motor spindle 155 and the ball nut 210, and transmits the steering assisting power generated by the motor 150 in proportion to the steering torque applied to the steering wheel to the rack bar 140 through the ball nut 210.
The rack driving type power steering apparatus of the prior art as illustrated in FIGS. 2a and 2b includes: a rack bar 140 provided with a peripheral screw flute 145 on the outer periphery thereof; a ball nut 210 having a intermediate path 215; balls 220 adapted to be moved by rolling while being in contact with the outer peripheral screw flute 145 of the rack bar 140 and the intermediate path 215, the balls 220 being circulated through the intermediate path 215; and an end cap 230 attached to an end of the ball nut 210.
The rack-driving type power steering apparatus causes the rack bar 140 to slide as the balls 220 are moved by rolling while being in contact with the outer peripheral screw flute 145 of the rack bar 140 and the inner peripheral screw peripheral flute of the ball nut 210.
In addition, a pinion shaft 110 and a torque sensor 239 are coupled to the rack housing 120, and a connector 241 of a wire harness 243 inserted through a side of the rack housing 120 is coupled to the torque sensor 239, and then a bearing 237 is coupled to the pinion shaft 110.
When the pinion shaft 110 and the torque sensor 239 are coupled to the rack housing 120 in this manner, a rack housing cover 235, to the top of which a sealing member 245 is coupled, is coupled to the rack housing 120 by fastening members, thereby completing the assembly.
However, such a conventional electric power steering apparatus has problems in that due to a number of constitutional elements, assembling steps are increased which in turn increases manufacturing costs, and due to the accumulation of assembling errors of many constitutional elements, an error may occur in measuring a torque change.